What is AQL, Inspection Level, and Type of Inspection

T

tahashamim

#1
Dear All,

I was going through "sqconline" website and it is asking for Inspection Level, AQL, and Type of Inspection. Can someone please walk me through with a practical example.

Such as what is the difference among reduce, normal, and tightened inspection type and what is the difference among difference levels and how should we intend to bring them in practice...

By the way, we are contract electronic assembly manufacturer and we have 100% final inspection. Before these assembeled boards get to final inspeciton, some of them also get functional test and go through "AOI - Automated Optical Inspection" for some defects, such as damaged components, wrong polarity, wrong components, missed components.

Generally the steps are as follows,

1- SMT (Electronic machine that places components and solder them)
2- Visual inspeciton on boards by quality inspector. (May go to AOI)
3- Through Hole (Manual placement of components on board
4- Wave soldering
5- Post Wave visual inspeciton
6- Manual Assembly
7- 100% Visual Inspection

So we would like to reduce this final 100% inspection. Any help. I am sure you all gurus will probably have more questions, so please feel free to ask so I can get all the help I can.

By the way, I went through this website whole day yesterday to find what I was looking for and did not really find what I was looking for.

Thanks in advance.

Taha.
 
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BradM

Staff member
Admin
#2
Taha, I am very sorry that I let your post go without a response! We sure are glad that you dropped by the Cove here for your question.:yes:

As far as reduced, normal, and tightened inspection-that is related to the failures detected in your inspection process. Assume you start at normal inspection. After your inspect several times, you find that your inspections repeatedly pass under the inspection plan that you have in-place. Thus, your process is in control, and the inspection plan can be relaxed. You can continue on the reduced inspection, until there is a failure (under the plan). Then you proceed back to normal. If there is a failure under normal, then chances are high that something has changed in your process, and closer monitoring is in order. Thus, under tightened inspection, the inspection is held to a tighter requirement than the other two. If under the tightened you have repeated passes, you can return to normal, and so on. You can write three dots beside each other, and draw an "eight" shape among the three showing the inspection-plan path.
 
T

tahashamim

#3
Thank you Brad,

I am actullay trying to find out the difference among Reduce, Normal, and Tightened inspection levels etc.

Can you or someone else give me an example from their industry or company? For example if a part has to be inspected for its length, width, and height, how will normal, reduce, and tightened inspection level play the role?

Consider me as a layman in quality and explain me with examples as we explain children...lol

Thanks,
Taha.
 

GStough

Staff member
Super Moderator
#5
Thank you Brad,

I am actullay trying to find out the difference among Reduce, Normal, and Tightened inspection levels etc.

Can you or someone else give me an example from their industry or company? For example if a part has to be inspected for its length, width, and height, how will normal, reduce, and tightened inspection level play the role?

Consider me as a layman in quality and explain me with examples as we explain children...lol

Thanks,
Taha.
Hi Taha and welcome to the Cove!

Here is an example from my previous place of employment:

We received raw materials from approved suppliers, which we inspected upon arrival. When using a new suppier, we began inspection of goods with the normal inspection plan. After having inspected a certain number of shipments which met the AQL of the normal inspection plan, we then moved that supplier to a reduced inspection plan, which meant that we would inspect fewer samples with each shipment we received. However, if a problem was found with the raw materials when we used the reduced inspection plan, then we moved this supplier to the tightened inspection plan. This means that we inspected a greater number of samples than we originally had with the normal inspection plan. When the supplier pulled the quality back into line and the number of defects found decreased, then we would move them to the normal inspection plan again. This cycle would continue throughout the whole period of time that we used this supplier.

I know this is rather lengthy, but I hope it helps illustrate how these inspection plans are used. :)
 
T

tahashamim

#6
Thanks to both Stijloor and GStough,

I am reading what Stijloor has sent the link for and on GStough post, it would mean that reduced, tightened, and normal inspection type means the quantity of samples and has nothing to do with the attributes of a material.

Now whats up with "Inspection Levels"?

By the way thanks to all who have responded and who have read it.

Thanks,
Taha
 

GStough

Staff member
Super Moderator
#7
Thanks to both Stijloor and GStough,

I am reading what Stijloor has sent the link for and on GStough post, it would mean that reduced, tightened, and normal inspection type means the quantity of samples and has nothing to do with the attributes of a material.

Now whats up with "Inspection Levels"?

By the way thanks to all who have responded and who have read it.

Thanks,
Taha
Yes, Taha, reduced, tightened and normal (as well as skip-lot and other types) all relate to the quantity of samples inspected and have nothing to do with the attributes of the material - this is something that should be in your specifications for the material.

Hang in there and keep plugging away at it. You're doing great! :tg:
 
T

tahashamim

#9
Great!


It is very true that we must understand it correctly before implementing them.

Are there any books on sampling plans for "idiots" [like myself] lol. Meaning it explain things very clearly in a simple way.

I am going through internet, but do not want to spend money on a book which I am not sure will be very useful in the end or not.

Once again thank u all.

Taha.
 

GStough

Staff member
Super Moderator
#10
Great!


It is very true that we must understand it correctly before implementing them.

Are there any books on sampling plans for "idiots" [like myself] lol. Meaning it explain things very clearly in a simple way.

I am going through internet, but do not want to spend money on a book which I am not sure will be very useful in the end or not.

Once again thank u all.

Taha.
If you have a public library or a local ASQ section, either of these would be excellent free resources. :agree1:
 
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